The present invention relates to a threading mechanism in a magnetic writing/reading apparatus, and more particularly to a threading mechanism in a magnetic writing/reading apparatus by which a leader pin, fitted to one end of a magnetic recording tape, is taken out of a tape cartridge, and shifted to a prescribed guide path to thread the magnetic recording tape onto a reel in the apparatus.
Related Art
In a conventional threading mechanism, when a tape cartridge is loaded and the magnetic tape therein is pulled out of the tape cartridge, the leader pin fitted to one end of the magnetic tape is held to a leader block by a threader drive, and the leader pin is guided to a reel by way of a guide path.
In order to ensure smooth threading, the leader block should be freely rotatable relative to the arm shaft. When the tape is being pulled, the leader block is pulled by the tape toward the tape cartridge and the operation is thereby stabilized. However, if the tape comes off the leader block while it is being threaded, the leader block will turn and be made unable to be inserted into the tape cartridge, and the apparatus can no longer function as such.
Further, the leader block should turn within the take-up reel together with the reel. To enable them to turn, there should be a gap between the arm shaft and the leader block. For this purpose, merely providing a guide cannot stabilize the operation of the leader block, resulting in difficulty to insert it into the cartridge.
FIG. 6 comprise FIG. 6A, which shows a plan of a tape cartridge in the magnetic tape device of a magnetic writing/reading apparatus, and FIG. 6B, which shows a front view of the same.
In a tape cartridge 50 is accommodated a tape 50b on which magnetic records are to be written. At the tip of the tape 50b is provided a leader pin 50a for use in pulling the tape out of the tape cartridge 50.
FIGS. 7 through 9 illustrate an example of the conventional art disclosed in the Japanese Patent Application Laid-open No. 2001-135003. FIG. 7 shows a plan of the threading mechanism of a magnetic writing/reading apparatus. FIG. 8 illustrates apart of the threading mechanism in which an arm 131 and a leader block 133 are arranged.
A loader drive gear 111 turns in the direction of arrow E, and a threader drive gear 112 coupled to the loader drive gear 111 turns in the direction of arrow F. Then a roller 123 fitted to the arm 131 passes a cam groove 124 provided in the threader drive gear 112 and reaches a cam groove end 125. Along with that, a roller 126 shifts along a guide groove 127 provided in a plate 134. As a result, the arm 131 and the leader block 133 at its tip shift. During the shift, the leader block 133 is free to rotate.
The leader block 133 is freely rotatable relative to an arm shaft 131a. If the leader block 133 is moved with the arm shaft 131a in this state, the direction of the leader block 133 cannot be stabilized.
The leader pin 50a of the magnetic tape is engaged with and held by hooked parts 80a provided at both the top and the bottom of the leader block 133. However, engagement with such simple hooked parts cannot securely hold the leader pin 50a. For this reason, a structure in which the force to hold the leader pin 50a is enhanced is conceivable.
FIG. 9A and FIG. 9B illustrate the structure of the leader block of such a threading mechanism.
A leader block 80 is fitted with a spring 81. When the leader pin 50a enters the hooked parts 80a, it is pressed against the leader block 80 by the spring 81, resulting in an enhanced holding force.
However, a threading mechanism of this structure would involve the following problems.
First, if the tape comes off during operation, the device will lose its mechanical function, because the leader block would then be freed and its direction destabilized, making it impossible to return the leader block into the cartridge merely by moving the arm.
Second, the shape of the leader block is made complex as shown in FIG. 8, and the cost of parts will increase correspondingly, because a rotary part should be added to the arm shaft part to prevent the leader block from interfering with the cartridge when the base is loaded with the cartridge.
Third, the insecure holding of the leader pin against the leader block makes it more likely to come off the leader block, because the leader pin is supported only by the hooked parts of the leader block. Even if a structure in which springs are fitted to the leader block is used, after repeated engagement and disengagement of the leader pin, the hooked parts of the leader block may be broken, because every time the leader pin is engaged or disengaged, the leader pin and the leader block come into friction with each other and, moreover, the shape of the leader pin requires the hooked parts to be thin. As a result, repetition of the engagement and disengagement of the leader pin would make it impossible to record data on the magnetic tape, because the wear due to the engagement and disengagement would scrape the leader block to generate dust. Thus, dust coming between the tape and the head would create a gap, which would make recording impossible.